Numerical and experimental study on scaled soil-structure model for small shaking table tests

The goal of this study is to determine an appropriate geometric scaling coefficient for small-capacity shaking table tests representing the full-scale field conditions rigorously for the soil-structure interaction (SSI) problem. SSI effects on the dynamic response of the mid-rise reinforced concrete structures placing on silty sand soil under different earthquake motions for both actual system and scaled test model were directly analyzed by using 2D finite element method under plane-strain condition. Three different earthquake acceleration records as Chi-Chi (1999), Loma Prieta (1989) and Kocaeli (1999) have been considered at the bedrock level of the soil-structure system for this study. In the first phase of this work, the representation capacity of the employed scaling factor of 1:45 are evaluated by comparing the structural lateral displacements obtained from the fixed-base and flexible base analysis for full-scale field conditions with those for scaled test model to be experimentally examined in the small-capacity shaking table. The scaled geotechnical model is composed of the undisturbed soil specimen taken from the real site and the laminar soil container designed to be formed of aluminum frames and rubber layers. Afterward, the obtained results from the scaled numerical model of the soil-structure coupled system have been validated and verified by those of employing experimental shaking table tests. According to the obtained numerical and laboratory test results, it is concluded that the carefully selected large geometric scale coefficients for the soil-structure model used in the small-scale shaking table experiments can capture the dynamic response of the full-scale soil-structure system with acceptable accuracy. It is clearly observed that the local soil properties have considerably amplified the earthquake response of the structures in comparison to the fixed base structure. Furthermore, the structural behavior is significantly affected by the frequency content of the earthquakes considered in the SSI problem.